Viscous sensor

ABSTRACT

A viscous end-of-run and jam sensor and indicator for a cassette-type motion picture camera. A drag disk is mounted for rotation about the axis of rotation of the film take-up assembly and has a drag surface in closely-spaced juxtaposition with a rotatably-driven annular surface of the film take-up assembly. A quantity of viscous fluid is disposed between the drag surface and the rotatably-driven surface to form a viscous coupling therebetween to impart torque to the drag disk during rotation of the film take-up assembly. The drag surface and the rotatablydriven surface have continuous peripheral portions which define a small acute angle of divergence sufficient to effect retention of the viscous fluid between the drag surface and the driven surface by capillary attraction. A bias spring maintains the drag disk in a predetermined quiescent position in the absence of rotation of the film take-up assembly. An electrical circuit includes in series connection a voltage source, a manually-actuatable cameraactuation switch, a sensing switch, and an indicator lamp. The sensing switch is maintained closed by an arm extending from the drag disk when the drag disk is in its quiescent position. The indicator lamp thus will be energized in response to a cessation of rotation of the film take-up assembly due to the end of the run of the film or a film jam occurring while the cameraactuation switch is closed.

'United States Patent 1 L LaRue, Jr. I I Y I I [5 1 VISCOUS SENSOR [75]lnventorz Mervin W. LaRue, Jr., Barrington,

Ill. v i

[73] Assignee: Bell & Howell Company, Chicago, Ill.

22 Filed: July 3, 1972 [21] Appl. No.: 268,838

[52] US. Cl. 2.42/191, 192/58 R, 192/107 M,

. ZOO/61.17, ZOO/61.39, 242/57 [51] Int. Cl B65h 25/32 [58] Field ofSearch 242/191', 57; 200/61.17,

ZOO/61.16, 61.15, 61.18, 61. 39, 33; 307/120, 141,192/56 F, 58 R, 107 M[56] References Cited I Primary Examiner-George F.. Mautz u-11 13,825,207 [451 July23, 1974 [5 7 ABSTRACT A viscous end-of-run and jamsensor and indicator for a cassette-type motion picture camera." A'dragdisk is mounted for rotation about the axis of rotation of the filmtake-up assembly and has a drag surface in closely-spaced juxtapositionwith a rotatably-driven annular surface of the film take-up assembly. Aquantity of viscous fluid is disposed between the drag surface and therotatably-clriven surface to form a viscous coupling therebetween toimpart torque to the drag disk during rotation of the film take-upassembly. The drag surface and the rotatably-driven surface havecontinuous peripheral portions which define a small acute angle ofdivergence sufficient to effect retention of the viscous fluid betweenthe drag surface and the driven surface by capillary attraction. A biasspring maintains the drag disk in a predetermined quiescent position inthe absence of rotation of the film take-up assembly.

An electrical circuit includes in series connection a voltage source, amanually-actuatable cameraactuation switch, a sensing switch, and anindicator lamp. The sensing switch is maintained closed by an armextending from the drag disk when the drag disk 11 Claims, 4 DrawingFigures v scous SAENSORV This invention relates to a viscous sensor and,in particular, to a viscous sensor for web handling mechanisms. Incertain web handling mechanisms, a rotary assembly is provided to takeup the web or film which has been passed through the mechanism bywinding the same onto a reel. Inmany instances, operation of themechanism can be significantly facilitated if the instantaneous rotarycondition of the take-up assembly can continuously be sensed for thepurpose of providing an alarm or control signal. For example, in acassette-type motion picture camera, the sensing of a cessation ofrotation of the film take-up assembly during camera operation may beused to initiate an alarm signal indicating that the end of the film hasbeen reached or that the film has jammed. It is-a principal object ofthe present invention to provide viscous meansfor sensing cessation ofrotation in'a rotary. assembly ofaweb handling mechanism. g The presentinvention incorporates a drag element mounted for rotation about theaxis of the web or film takeup assembly andfhaving a drag surfaceincloselyspaced juxtaposition with a rotatably-driven surface of 2 I.FIG. 1 is an elevational view of ment of the present invention. l

FIG. 2 is across-sectional view taken along lines 2-2 of FIG. 1.

FIG. 3 is an enlarged view of a portion of FIG. 2. FIG. 4 is anisometric view to illustrate the positioning of a leaf spring retainingmember used in the preferred embodiment.

Referring now to the drawings, a preferred embodiment of the inventionis shown for providing an end-ofrun and jam alarm signal in a motionpicture camera.

a preferred embodi- 'The structure is mounted in a housing or frame of amotion picture camera in association with the film take-up assembly ofthe camera.

The camera take-up assembly includes an input drive shaft 12 journaledthrough a positioning member 14 inthe-take-up assemblypA quantity offluid having a selected' viscosity characteristic is disposed betweenthe drag surface and thedriven surface to form a viscous coupling forimparting torque from the take-up assem bly to the'drag-element. Meansresponsive to the drag elementare provided to generate an indicatingsignal.

A troublesome problem attendingthe provision of a viscous coupling isthat of retaining the viscous fluid between the drag surface and thedriven surface without leakage. Accordingly, itis another importantobject of the present invention to provide a leak-proof viscouscoupling. This is achieved in the present invention by providinga dragsurface and a driven surface which are compatibly configured to havecontinuous peripheral portions defining an acute angle of divergence toeffect retention of the viscous fluid between the'drag surface and thedriven surface by capillary attraction.

Additional features of the present invention include the provision ofbias means effective to maintain the drag element in a predeterminedquiescent position restrained against movement in the direction ofrotation of the take-up assembly when the rate of rotation of therotatably driven surface of the take-up assembly is less than apredeterminedrate and the provision of electrical circuitmea'nsincluding switch means responsive to the posit-ion of the'dragelement toprovide a signal indicative of the rotary condition of the take-up assembly. Preferably, the switch means comprises a switch which is adapted tobe opened when sufficient torque is imparted to the drag element by thetake-up assembly, and closed by the drag element when the drag elementis in its quiescent position, closure of the switch being effective toproduce a'signal indicating thatthe rate of rotation of thetake-upassembly is less than a predetermined rate.

These and other features and objects of the present invention will bebetter understood by reference to the ings.

IN THE DRAWINGS:

following detailed description and'the appended drawtegral with thehousing 10. The shaft 12 is driven bythe camera drive (not shown) and isprovided with a wormthreaded end portion 16 for driving a gear ring 18in worm-gear driving engagement.

The gear ring 18 is rotatably mounted on an output take-up shaft 20which is rotatablyjournaled at one end in an opening 22 in the housing10 for rotatably driving a take-up reel driving disk 24. The reelmounting disk 24 is affixed to the take-up shaft 20 by acoaxiallypositioned screw 26 or other suitable-fastening means andincludes suitable reel driving-elements 28.

The take-up shaft 20 is supported and positioned at its opposite end bya coaxial bearing pin 30 which is passed through an elongate bracket 32and received within a central axial bore 34 in the take-up shaft 20.

The bracket 32 is affixed ateach end to the camera housing 10 by screws36 or other suitable fastening means. A bearing bushing 38 is interposedbetween the bracket 32'and The gear ring 18 is provided on one side withan annular cavity 40 within which a radially extending integral annularflange 42 of the take-up shaft 20 is partially received. On its oppositeside, the gear ring 18 is positioned by a disk 46 which is also mountedon the shaft 20. A leaf spring retaining member 48 is keyed to both theshaft 20 and the retaining disk 46 and serves to bias boththe disk 46and the flange 42 into frictional engagement with the gear ring 18. Asdepicted in FIG. 4, the exterior projections 49 and 50 of the leafspring retaining member 48 are received withinthe slots 51 and 53,respectively, of the retaining disk 46. The interthe associated end ofthe take-up shaft ior projections 55 and 57 of the retaining'member 48 Iare received within slots 59 and 61, respectively, provided in thetake-up shaft 20(see FIGS. 2 and 4). In this manner the retaining member48 is keyed to both the take-up shaft 20and the retaining disk 46. Inposi-' tion, the leaf spring retaining member is bowed resiliently (seeFIG. 4) to develop the requisite bias force urging both the disk 46 andthe take-up shaft flange 42 into frictional engagement with the gearring 18 for frictionaltransmission of torque from the driven gear ring18 to the take-up shaft'20. A drag disk 52 is rotatably mounted on anannular collar 54 of the take-up shaft 20 toprovide an annular dragsurface 56 in juxtaposition with the annular driven 3 gion therebetweenin which a quantity of viscous fluid 62 is disposed. The fluid 62 has aviscosity sufficient to form a viscous coupling between the drag surface56 and the annular driven surface 58 for imparting slip torque from thetake up shaft 20 to the drag disk 52.

It is important to note that the annular crowned surface 58 of thetake-up flange 42 and the planar drag surface 56 of the drag disk 52 arecompatibly configured to have continuous annular peripheral portions 64and 68 alongv their outer periphery which cooperate to define a smallacute angle X of divergence radially outwardly and continuous annularperipheral portions 66 and 70 which cooperate to define a small acuteangle X of divergence radially inwardly. The acute angles X and X aresufficient to effect leak-proof retention of the viscous fluid 62between the drag surface 56 of the drag disk 52 and the annular drivensurface 58 of the take-up shaft flange 42 by capillary attractioneliminating the need for additional sealing rings and the like. Theangles X and X are preferably, but not necessarily, equal to oneanother. It is apparent that either or both the annular driven surface58 and the drag surface 56 may be suitably crowned, beveled, orotherwise provided with inclined peripheral'portions to cooperativelydefine the requisite angles of divergence X and X for viscous fluidretention. In the exemplary embodiment shown, the drag surface 56 isplanar, and the annular driven surface 58 is inclined radially outwardlyat portion 64 from an annular crown 72 to the outer diameter of thedriven surface 58 and is inclined radially inwardly at portion 66 fromthe annular crown 72 to the inner diameter of the driven surface 58. Inthis connection, it should further be noted that the inner and outerdiameters of the driven surface 58' are preferably, but not necessarily,equal to the inner and outer diameters, respectively, of the dragsurface 56.

The drag disk 52 is provided with an integral radially extending arm 74which is biased by an elongate coil spring 78 toward a predeterminedlimit position (shown in elevation in FIG. 1) against the body of asensing switch 76 rigidly affixed to the housing 10 of the camera. Theelongate coil spring 78 is engaged at one end to an engagement member 80which is rigidly affixed to the housing l of the camera. The oppositeend of the spring 78 is engaged in a recess 82 in the dragdisk arm 74,and the spring 78 is arranged in a C- shaped configuration as depictedin FIG. 1 to develop a bias force in the direction indicated by thearrow 84.

The sensing switch 76 is provided with contacts 86 and 88 which areconnected in series with the normally open contacts 94 and 96 of acamera-actuation or control switch 90-mounted to the camera housing andadapted to be closed by manual depression of the asso- .ciatedcamera-actuation button 92. The camera- In operation with thecamera-actuation switch closed by manual depression of the button 92,rotation of the filmtake-up shaft 20 at normal speeds will impart to thedrag disk 52 a slip or drag torque in the direction indicated by thearrow 102 sufficient to partially rotate the drag disk 52 and angularlydisplace the extending arm 74 away from the limit position shown inelevation in FIG. 1 and against the bias exerted by the spring 78,thereby opening the sensing switch 76. More specifically, the extendingarm 74 will be displaced to an equilibrium position as shown in phantomview in FIG. 1 at which the drag torque imparted to the drag disk 52 bythe viscous coupling is in equilibrium with the increased bias forcedeveloped by the bias spring 78.

Should the take-up shaft begin rotating at an abnormally low rate orcease rotating entirely due to the occurrence of the end of the run orto a film jam while the camera-actuation switch 90 is closed, the biasspring 78 will return the arm 74 to its limit position, closing thesensing switch 76 to complete the series circuit and therebyenergizingthe indicator lamp 99 to provide a visual alarm signal to theoperator. Whether an alarm indication will be given only when thetake-up shaft stops entirely or also when the rate of rotation of thetake-up shaft falls below a predetermined minimum rate will depend uponthe design level of bias force to be exerted by the bias spring 78 andother related design parameters.

It will be apparent to those skilled in the art that the particularembodiment shown and described herein by way of example may be modifiedin various respects without departing from the scope of the inventiveconcepts.

What is claimed is:

1. In a web handling mechanism having a rotatably driven member, thecombination therewith of a sensor comprising:

a rotatably mounted drag element having a drag surface in closely spacedjuxtaposition with an adjacent surface of said rotatably driven member;

, a quantity of fluid having a selected viscosity characteristicdisposed between said drag surface and said adjacent surface of saidrotatably driven member to form a viscous coupling, said drag surfaceand said adjacent surface being compatibly configured to have continuousperipheral portions defining an acute angle of divergence to effectretention of said viscous fluid between said drag surface and saidadjacent surface by capillary attraction; and

signal producing means responsive to said drag element for providing anindicating signal.

2. The invention defined in claim 1 wherein said drag surface and saidadjacent surface of said rotatably driven member are substantiallyradially oriented surfaces, at least one of said radially orientedsurfaces having an inclined portion to provide said acute angle ofdivergence.

3. The invention defined in claim 1 further comprising resilient meansaxially urging said drag element toward said adjacent surface of saidrotatably driven member.

4. The invention defined in claim 1 further comprising bias meanseffective to maintain said drag element in a predetermined positionrestrained against rotative movement when the rate of rotation of saidrotatably driven member is less than a predetermined rate, said itsignal producing means being responsive to departure of said dragelement from said predetermined position to provide a signal indicatingthat the rate of rotation of said rotatably driven member is less thansaid predetermined rate.

5. In a web handling'mechanism having a rotatablydriven web take-upassembly, the combination therewith of a sensor comprising: v

a drag disk mounted for rotation about the axis of said web takeupassembly and having an annular radially oriented drag surface in closelyspaced juxtaposition with an annular rotatably driven radially 1oriented surface of said web take-up assembly; a quantity of fluidhaving a selected viscosity characteristic disposed between said annulardrag surface and said annular rotatably driven surface to form a viscouscoupling, said annular drag surface and said annular rotatably drivensurface cooperating to define an annular drag transmission region havingan inner annular periphery and an outer annular periphery, said annulardrag surface and said annular rotatably driven surface being compatiblyconfigured continuously along said inner and outer annular peripheriesto define a small acute angle of divergence sufficient to'effectretention of said viscous fluid within said drag forcetransmission.region by capillary attraction; means urging said drag elementv towardsaid annular rotatably driven surface; bias means effective to maintainsaid drag element in a quiescent position restrained against rotation inthe direction of rotation of said web take-up assembly when the rate ofrotation of said rotatably driven surface is less than a predeterminedrate, said drag element being maintained in an equilibrium position whensaid rotatably-driven surface is equal to said predetermined rate; andelectrical circuit means, including switch means responsive to theposition of said drag element, for providing an output signal.

6. The invention defined in claim 5 wherein at least oneof said annularsurfaces includes inclined portions to provide said small acute angle ofdivergence along said inner annular periphery and along said outerannular periphery.

7. The invention defined in claim 5 wherein said switch means include aswitch adapted to be opened when said drag element is maintained in saidequilibrium position, and closed when said drag element is in saidquiescent position, closure of said switch being effective to'produce asignal indicating that the rate of rotation of said web take-up is lessthan said predetermined rate.

8. In a motion prising:

picturecamera, the combination com-.

, I 6 a'drive film take-up shaft; g

a radially extending annular flange affi'xed to said take-up shaft;

a drag disk rotatably mounted on said shaft in closely spacedjuxtaposition with said annular flange and having an extending arm; v I

resilient means biasing said drag disk axially toward said annularflange; I ,5

' a quantity of fluid having a selected viscosity characteristicdisposed between said drag disk and said annular flange to form aviscouscoupling, said annular flange and said drag disk being compatiblyconfigured to have continuous peripheral portions to define a smallacute angle of divergence suffi cient to effect retention of saidviscous fluid between said annular flange and said drag disk sufficientto impart drag torque to said drag disk during rotation of said take-upshaft; I I

bias means effective to maintain said drag disk in a predeterminedquiescent position in the absence of rotation of said film take-upassembly, and

an electrical circuit including in series connection a voltage source, afirst camera-actuation switch, a second switch disposed in'proximity tosaid extending arm when said vdrag disk is in said predeterminedquiescent position, wherebysaid indicator lamp will be energized inresponse to a cessation of rotation of said film 'take up shaft whilesaid camera-actuation switch is closed.

9. The invention defined in claim 8 wherein said drag disk is.configuredto present an annular planar drag surface in juxtaposition tosaid annular flange, said drag surface having an inner diametersubstantially equal to the inner diameter of said annular flange and anouter diameter substantially equal to the outer diameter of said annularflange, and wherein said annular flange, in turn, is configured topresent an annular crowned surface in juxtaposition to said drag surfaceof said drag disk, said crowned surface being divergently inclined atsaid small acute angle in proximity of said outer diameter of saidannular flange, said crowned surface further being divergently inclinedat said small acute angle proximity of said inner diameter of saidannular flange.

into closing engagement with said second switch.

1. In a web handling mechanism having a rotatably driven member, thecombination therewith of a sensor comprising: a rotatably mounted dragelement having a drag surface in closely spaced juxtaposition with anadjacent surface of said rotatably driven member; a quantity of fluidhaving a selected viscosity characteristic disposed between said dragsurface and said adjacent surface of said rotatably driven member toform a viscous coupling, said drag surface and said adjacent surfacebeing compatibly configured to have continuous peripheral portionsdefining an acute angle of divergence to effect retention of saidviscous fluid between said drag surface and said adjacent surface bycapillary attraction; and signal producing means responsive to said dragelement for providing an indicating signal.
 2. The invention defined inclaim 1 wherein said drag surface and said adjacent surface of saidrotatably driven member are substantially radially oriented surfaces, atleast one of said radially oriented surfaces having an inclined portionto provide said acute angle of divergence.
 3. The invention defined inclaim 1 further comprising resilient means axially urging said dragelement toward said adjacent surface of said rotatably driven member. 4.The invention defined in claim 1 further comprising bias means effectiveto maintain said drag element in a predetermined position restrainedagainst rotative movement when the rate of rotation of said rotatablydriven member is less than a predetermined rate, said signal producingmeans being responsive to departure of said drag element from saidpredetermined position to provide a signal indicating that the rate ofrotation of said rotatably driven member is less than said predeterminedrate.
 5. In a web handling mechanism having a rotatably-driven webtake-up assembly, the combination therewith of a sensor comprising: adrag disk mounted for rotation about the axis of said web take-upassembly and having an annular radially oriented drag surface in closelyspaced juxtaposition with an annular rotatably driven radially orientedsurface of said web take-up assembly; a quantity of fluid having aselected viscosity characteristic disposed between said annular dragsurface and said annular rotatably driven surface to form a viscouscoupling, said annular drag surface and said annular rotatably drivensurface cooperating to define an annular drag transmission region havingan inner annular periphery and an outer annular periphery, said annulardrag surface and said annular rotatably driven surface being compatiblyconfigured continuously along said inner and outer annular peripheriesto define a small acute angle of divergence sufficient to effectretention of said viscous fluid within said drag force transmissionregion by capillary attraction; means urging said drag element towardsaid annular rotatably driven surface; bias means effective to maintainsaid drag element in a quiescent position restrained against rotation inthe direction of rotation of said web take-up assembly when the rate ofrotation of said rotatably driven surface is less than a predeterminedrate, said drag element being maintained in an equilibrium position whensaid rotatably-driven surface is equal to said predetermined rate; andelectrical circuit means, including switch means responsive to theposition of said drag element, for providing an output signal.
 6. Theinvention defined in claim 5 wherein at least one of said annularsurfaces includes inclined portions to provide said small acute angle ofdivergence along said inner annular periphery and along said outerannular periphery.
 7. The invention defined in claim 5 wherein saidswitch means include a switch adapted to be opened when said dragelement is maintained in said equilibrium position, and closed when saiddrag element is in said quiescent position, closure of said switch beingeffective to produce a signal indicating that the rate of rotation ofsaid web take-up is less than said predetermined rate.
 8. In a motionpicture camera, the combination comprising: a drive film take-up shaft;a radially extending annular flange affixed to said take-up shaft; adrag disk rotatably mounted on said shaft in closely spacedjuxtaposition with said annular flange and having an extending arm;resilient means biasing said drag disk axially toward said annularflange; a quantity of fluid having a selected viscosity characteristicdisposed between said drag disk and said annular flange to form aviscous coupling, said annular flange and said drag disk beingcompatibly configured to have continuous peripheral portions to define asmall acute angle of divergence sufficient to effect retention of saidviscous fluid between said annular flange and said drag disk sufficientto impart drag torque to said drag disk during rotation of said take-upshaft; bias means effective to maintain said drag disk in apredetermined quiescent position in the absence of rotation of said filmtake-up assembly; and an electrical circuit including in seriesconnection a voltage source, a first camera-actuation switch, a secondswitch disposed in proximity to said extending arm when said drag diskis in said predetermined quiescent position, whereby said indicator lampwill be energized in response to a cessation of rotation of said filmtake-up shaft while said camera-actuation switch is closed.
 9. Theinvention defined in claim 8 wherein said drag disk is configured topresent an annular planar drag surface in juxtaposition to said annularflange, said drag surface having an inner diameter substantially equalto the inner diameter of said annular flange and an outer diametersubstantially equal to the outer diameter of said annular flange, andwherein said annular flange, in turn, is configured to present anannular crowned surface in juxtaposition to said drag surface of saiddrag disk, said crowned surface being divergently inclined at said smallacute angle in proximity of said outer diameter of said annular flange,said crowned surface further being divergently inclined at said smallacute angle proximity of saId inner diameter of said annular flange. 10.The invention defined in claim 9 wherein said bias means comprises acoil spring fixedly positioned at one end and engaged at its oppositeend with said extending arm of said drag disk.
 11. The invention definedin claim 10 wherein said coil spring is arranged in a C-shapedconfiguration biasing said extending arm of said drag disk in adirection opposite to the direction of rotation of said take-up shaftand toward said predetermined quiescent position into closing engagementwith said second switch.